Sediment Stress in an Extensional Basin with Pre-Existing Fault and Salt Roller

Autor: M. A. Nikolinakou, M. Heidari, M. R. Hudec, P. B. Flemings
Rok vydání: 2022
Zdroj: All Days.
DOI: 10.56952/arma-2022-0547
Popis: ABSTRACT: We study sediment stress in an extensional basin with a critically oriented pre-existing fault and an underlying salt layer using forward geomechanical models. We first identify stress changes in a basin without salt. We show that the presence of a fault with lower frictional resistance than the intact sediment leads to re-orientation of principal stresses near the fault, and abrupt changes in the minimum principal stress across the fault. Sediment rollover in the hanging wall leads to stress arching, which reorients principal stresses in the upper parts of the hanging wall despite the ongoing extension. When salt underlies the sediment basin, a salt roller develops at the location of the fault and minimizes sediment rollover in the hanging wall. Loading from the rising diapir increases horizontal stress in the hanging wall. The angled salt face also transmits higher overburden stresses from deeper parts of the basin to the shallow footwall area and loads the footwall sediments. We built these transient evolutionary simulations with Elfen. We model salt as solid viscoplastic and model sediments as poro-elastoplastic material. 1. INTRODUCTION Several numerical studies have explored the geomechanical interaction between salt and its wall-rock sediments (see Nikolinakou et al. (2018) for a review). These studies couple salt flow with sediment deformation and, in transient analyses, porous fluid flow. However, they model sediments as a continuum. A large number of salt basins are located in extensional systems (rift basins, passive margins; e.g., Jackson and Hudec (2017)). Normal faults are key features in these extensional systems. Faults are often weak discontinuities: their frictional strength is lower than that of continuum sediments. They can alter the in-situ stress state, sediment porosity, and strength (e.g., Schultz (2019)). Consequently, they may affect the salt flow and evolution of the salt geometry. Here, we study a simple extensional basin with a pre-existing fault and an underlying salt layer. We use a large-strain, evolutionary model to simulate the regional extension, the development of a salt diapir, and the deformation along the critically oriented fault. We first identify stress changes in a basin without salt. Then, we study how the presence of a reactive diapir affects the stress state in both hanging wall and footwall.
Databáze: OpenAIRE